208 ACTIVE IMMUNIZATION 



polyvalent, i. e., composed of organisms derived from a number of 

 cases of the kind that is under consideration, or from one single case, 

 but not from the individual who is to be treated. As long as we know 

 so little of what vaccines may accomplish it is clear that our clinical 

 knowledge is not sufficient to decide such a question. We can only 

 speak theoretically, and theoretically we must admit the probable 

 existence of many strains of a given type of organism, and with this 

 the possibility of individual differences, so that upon this basis au- 

 togenous vaccines would, cceteris paribus, appear to be preferable to 

 stock vaccines. But as it is frequently and in some infections indeed 

 uniformly impossible to prepare an autogenous vaccine, we may 

 be forced to use stock material in many cases. 



The preparation of the majority of vaccines is conducted as follows: 

 Cultures are made from whatever source is available, i. e., from the 

 pus of abscesses, from acne pustules, the urine, blood, sputum, etc., 

 the culture medium being chosen in accordance with the type of 

 organism that is expected, or which a preliminary examination has 

 shown to be present. If only one type is found, the vaccine is made 

 from it, while in the event of a multiple infection, or in the presence 

 of contaminating saprophytic organisms, the predominating patho- 

 genic varieties are chosen, i. e., those which are recognized as being 

 pathogenic either by direct examination or by passage through an 

 animal. 1 



Having once secured an initial supply, it is then only necessary 

 to inoculate a sufficient number of tubes or flasks of agar, or serum 

 agar, and to incubate these as usual. With organisms that furnish 

 a prolific growth, incubation for twenty-four hours is sufficient, while 

 with the more delicate organisms, such as the streptococcus and 

 pneumococcus, it is advisable to wait for forty-eight to seventy- 

 two hours. At the expiration of this time a small amount of sterile 

 saline solution (10 c.c. to an ordinary agar slant) is poured into the 

 first tube and the growth gently scraped off with a platinum loop. 

 The emulsion is then poured into the next, from this into the follow- 

 ing, and so on, according to the number of tubes or the quantity of 

 vaccine which is to be prepared. 



1 In this connection I cannot condemn too strongly the use of some of the 

 so-called polyvalent and mixed vaccines which have been recently placed upon 

 the market with the most extravagant claims for their efficacy in the absence 

 of any proof of their value. 



